1. Field of the Invention
This invention relates to an apparatus for removing a sterilant from a sterilant containing atmosphere in a room or other enclosure. A method of removing hydrogen peroxide gas from a room following gaseous surface sterilisation.
2. Relevant Technology and Summary of the Invention
It is frequently necessary to sterilise the surfaces inside clean rooms in which pharmaceutical manufacturing processes are operated. Similar sterilising is also required in the biotechnology, biomedical and health care industries.
The traditional technique used for the sterilisation process has been to generate formalin vapour and allow this to remain in the room for a period of time and then using an air extraction system to remove the formalin by dilution until it is safe to re-enter the room. This technique although effective in reducing the bio-burden has the disadvantage that it leaves a residue of para-formaldehyde which is persistent and causes an unpleasant smell.
More recently it has been possible to use gaseous hydrogen peroxide as the sterilising agent. This has the advantage of breaking down to water and oxygen, and therefore does not leave a residue. When properly applied it is also a much faster process than fumigation with formalin but there is still the problem of removing the residual gas once sterilisation has been achieved.
With hydrogen peroxide it is generally true that the largest phase of a sterilisation cycle will be the time for aeration to remove the residual gas to a safe level. Frequently it is possible to use the room ventilation system to extract the air and residual hydrogen peroxide gas, but in some buildings this may not be possible. If for example there is a common extract system, with some percentage of re-circulation then the extracted air containing the hydrogen peroxide may be circulated back to other areas and under such circumstances it is desirable to have an alternative aeration technique.
As a good general rule it may be assumed that by doubling the air extraction rate after hydrogen peroxide sterilisation it is possible to halve the time required to remove the active gas.
Most of the commercially available hydrogen peroxide gas generators circulate the gas through the room to be sterilised and then back to the generator. The air that is returned to the generator is then processed and further amounts of hydrogen peroxide gas are added. At the end of a gassing phase of a sterilisation cycle the air continues to circulate through the gas generator but the returning hydrogen peroxide is decomposed in the generator to water and oxygen. This circulating process breaking down the hydrogen peroxide would eventually remove all of the active gas from the room, but as this circulating flow is small the time taken to reduce the gas concentration would be very long.
JP-A-11221443 discloses a method of reducing the release of hydrogen peroxide from a sterilisation chamber in which hydrogen peroxide is used as the active sterilant. The chamber has a vacuum pump for withdrawing gases from the chamber and discharging them to atmosphere. Catalytic converters are located in the conduit between the chamber and inlet to the pump and between the outlet to the pump and the outlet to atmosphere to convert hydrogen peroxide flowing in the conduit into oxygen and hydrogen to reduce the concentration of hydrogen peroxide released at the outlet.
DE-A-199 45 500 discloses a method and apparatus as described and illustrated for sterilising containers in a filling machine, which are intended for the filling in particular of liquid or pasty foodstuffs, wherein the containers are flushed with hydrogen peroxide (H2O2) immediately before the filling operation and the filling operation is carried out in a sterile environment, wherein the H2O2 contained in the exhaust air is decomposed to H2O2 and O2 in a catalyst, and wherein the resultant sterile air serves to remove the hydrogen peroxide from the containers. For optimisation in respect of efficiency, environmental compatibility and process safety there is provision for the sterile air to form a laminar flow in the interior of the filling machine and for it to be used to seal the filling chamber by the surplus air volume being released into the environment.
DE-A-36 42 674 A1 discloses the sterilisation of filling installations and packing installations used for packing foodstuff and in the pharmaceutical industries. Hydrogen peroxide is often used in such applications. The hydrogen peroxide can be broken down after use with the aid of a platinum or palladium catalyst. However such catalysts decline in effectiveness in a relative short period of use. This difficulty can be overcome by the provision of a catalyst support in which a support body consists of carbon particles bonded together without binder, the common particles comprising a first carbon fraction which forms the support skeleton and a second carbon fraction of highly porous activated carbon with an inorganic catalytically active substance, in particular noble metals and their compounds, applied to the support body and/or the activated carbon particles to break down hydrogen peroxide flowing through the body.
It is an object of this invention to provide an apparatus for removing the sterilant such as hydrogen peroxide from an atmosphere in a room containing the sterilant without causing the circulation used to remove the sterilant from the atmosphere to contaminate the room.
This invention provides an apparatus for removing a sterilant from a sterilant containing atmosphere of a room comprising an enclosure having an inlet to receive sterilant containing air from the room following sterilization of the room, an outlet to return air from which sterilant has been removed to atmosphere, a catalyst within the enclosure for removing sterilant from the air, means for drawing sterilant containing air from the inlet through the catalyst and thence to atmosphere and means to circulate air containing sterilant from the room during a room sterilization process through that part of the enclosure which is downstream of the catalyst to ensure sterility of that part of the enclosure for the sterilant removal phase.
Preferably a filter is located in the enclosure between the inlet and outlet to filter air passing therethrough.
More specifically the filter may be located downstream of the catalyst and to be sterilized by supplemental means for drawing sterilant through the enclosure downstream of the catalyst during the room sterilization process.
In any of the above arrangements the catalyst may be a carbon filter.
Also in any of the above arrangements the outlet may comprise a nozzle or nozzles for directing the stream of air from which sterilant has been removed into the atmosphere around the enclosure to create turbulence in the air.
The supplemental means to draw sterilant through the part of the enclosure downstream of the catalyst during the room sterilization process may comprise further fan means of relatively low throughput compared with the first mentioned fan means, the further fan means having a further inlet disposed in said enclosure on said downstream side of the catalyst to draw air containing sterilant from the atmosphere into the enclosure during the room sterilization process and to circulate air through the downstream side of the enclosure to sterilize that part of the enclosure, the air containing sterilant being released from the enclosure by said outlet from the enclosure.
The apparatus may be mounted on, wheels to be readily mobile.
The present invention provides a rapid method of removing the active gas from the room without the necessity of providing an additional extract system.